Which is the marker for lipid peroxidation:
**Core Concept**
Lipid peroxidation is a process in which free radicals attack lipids containing carbon-carbon double bond, especially polyunsaturated fatty acids (PUFAs), leading to cell damage. This process is a significant factor in the pathogenesis of various diseases, including atherosclerosis and neurodegenerative disorders.
**Why the Correct Answer is Right**
The correct marker for lipid peroxidation is malondialdehyde (MDA). MDA is a product of lipid peroxidation that is formed when the peroxidized lipid is cleaved. It is a stable compound that can be easily measured in tissues and body fluids, making it a useful marker for oxidative stress. MDA reacts with thiobarbituric acid (TBA) to form a pink-colored complex that can be quantified spectrophotometrically.
**Why Each Wrong Option is Incorrect**
**Option A:** Hydrogen peroxide is a reactive oxygen species (ROS) that can initiate lipid peroxidation, but it is not a marker for lipid peroxidation.
**Option B:** Superoxide dismutase is an enzyme that catalyzes the dismutation of superoxide into hydrogen peroxide and oxygen, but it is not a marker for lipid peroxidation.
**Option C:** Glutathione is an antioxidant that plays a crucial role in protecting cells from oxidative damage, but it is not a marker for lipid peroxidation.
**Clinical Pearl / High-Yield Fact**
Mnemonically remember the "Fenton reaction" to understand the initiation of lipid peroxidation: Fe²⁺ + H₂O₂ → Fe³⁺ + OH⁻ + OH⁺. This reaction involves the conversion of hydrogen peroxide to hydroxyl radicals, which are highly reactive and can initiate lipid peroxidation.
**Correct Answer:** MDA. Malondialdehyde.